Activated zeolite beta and its use for hydrocarbon conversion

ABSTRACT

The present invention relates to a zeolite beta catalyst characterized by critical limits of weak and strong acid species and exceptionally high catalytic activity. The catalyst is activated at a temperature effective to substantially reduce the concentration of strong acid species, i.e., hydronium cations, without substantially reducing the concentration of weak acid species, i.e., hydroxoaluminum cations, preferably following a calcining step wherein a synthesized zeolite beta catalyst containing a templating agent is calcined at a temperature in the range of from about 200° to 1000° C. in order to remove a substantial portion of the catalyst templating agent and an ion-exchanging step wherein the calcined catalyst is ion-exchanged with a salt solution containing at least one hydrogen forming cation selected from NH 4   +   and quaternary ammonium. Conversion processes utilizing the catalyst of the invention, including isomerization of paraffins and alkylaromatics and disproportionation of aromatics, also are disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. Ser. No.08/096,808, filed Jul. 26, 1993, now U.S. Pat. No. 5,393,718, which is adivision of U.S. Ser. No. 07/767,457, filed Sep. 30, 1991, now U.S. Pat.No. 5,258,570, which is a continuation-in-part of U.S. Ser. No.07/596,157, filed Oct. 11, 1990, now U.S. Pat. No. 5,095,169, which is acontinuation-in-part of U.S. Ser. No. 07/366,263, filed Jun. 12, 1989,and now abandoned, which is a division of U.S. Ser. No. 071175,332,filed Mar. 30, 1988, and now abandoned, all of which are incorporatedherein by reference thereto.

FIELD OF THE INVENTION

This invention relates to a crystalline microporous three-dimensionalsolid catalyst having the structure and composition of zeolite beta andat least one enhanced catalytic property and to the use of the catalystin hydrocarbon-conversion processes.

BACKGROUND OF THE INVENTION

A wide variety of hydrocarbon conversion processes encountered in thepetroleum refining industry are catalytic in nature, and many of theseprocesses use crystalline aluminosilicate zeolites as catalysts.Illustrative of such processes include, for example, dewaxing,hydrodewaxing, crocking, hydrocracking, alkylation, isomerization,aromatization, disproportionation and the like. Often, the products fromsuch hydrocarbon conversion processes, or portions thereof, are admixedas blending components to form motor fuels such as gasoline.

Crystalline aluminosilicate zeolites have been used in a variety ofcatalysts for the conversion of hydrocarbons. Both natural and syntheticcrystalline aluminosilicates have been employed. Often the zeolitescomprise a noble metal such as platinum or palladium. Included amongthese are the Type X and Type Y zeolites, ZSM-5 and ZSM-20 zeolites,mordenite, as well as zeolite beta.

U.S. Pat. No. 3,308,069 and Re. 28,341, both issued to Wadlinger et al.,disclose a method for preparing zeolite beta. The patents disclose thatzeolite beta is prepared from reaction mixtures containingtetraethylammonium hydroxide as the alkali and more specifically byheating in aqueous solution a mixture of the oxides or of materialswhose chemical compositions can be completely represented as mixtures ofthe oxides Na₂ O, Al₂ O₃, [(C₂ H₅)₄ N]₂ O, SiO₂ and H₂ O suitably at atemperature of about 75°-200° C. until crystallization occurs. Theproduct which crystallizes from the hot reaction mixture is separated,suitably by centrifuging or filtration, washed with water and dried. Thematerial so obtained may be calcined by heating in air or an inertatmosphere at a temperature in the approximate range of 400°-1700° F. orhigher so long as the temperature is not sufficient to destroy thecrystallinity.

U.S. Pat. No. 4,642,226, issued to Calvert et al., relates to a new andimproved form of crystalline silicate having the structure of zeolitebeta, to a new and useful improvement in synthesizing said crystallinesilicate and to the use of said crystalline silicate as a catalyst fororganic compound, e.g., hydrocarbon compound, conversion. The patentdiscloses the use of dibenzyldimethylammonium as a directing agent,i.e., templating agent, instead of tetraethylammonium hydroxide asdescribed above. The patent further discloses that the zeolite beta canbe ion-exchanged by conventional techniques with a salt solution.Following contact with the salt solution of the desired replacingcation, the zeolite is then preferably washed with water and dried at atemperature ranging from 65° to about 315° C. and thereafter may becalcined in air or other inert gas at temperatures ranging from about200° to about 600° C., preferably from about 200° to about 550° C. forperiods of time ranging from 1 to 48 hours or more to produce acatalytically active thermal decomposition product thereof. The patentdiscloses the use of zeolite beta in hydroisomerization of normalparaffins, when provided with a hydrogenation component, e.g., platinum.

U.S. Pat. No. 4,428,819, issued to Shu et al., discloses a processrelating to the hydroisomerization of catalytically dewaxed lubricatingoils using zeolite beta. The patent discloses that when the zeoliteshave been prepared in the presence of organic cations they arecatalytically inactive, possibly because the intracrystalline free spaceis occupied by organic cations from the forming solution. It is furtherdisclosed that the zeolites may be activated by heating in an inertatmosphere at 540° C. for one hour, for example, followed by baseexchange with ammonium salts followed by calcination at 540° C. in air.

U.S. Pat. No. 4,554,145, issued to Rubin, discloses a method for thepreparation of zeolite beta. In similar fashion to above cited U.S. Pat.No. 4,642,226, the patent discloses that the synthesized zeolite betacan be ion-exchanged with a salt and thereafter calcined in air or otherinert gas at temperatures ranging from about 200°-550° C. for periods oftime ranging from 1 to 48 hours or more to produce a catalyticallyactive thermal decomposition product thereof. The patent discloses theuse of zeolite beta in hydroisomerization of normal paraffins, whenprovided with a hydrogenation component, e.g., platinum.

U.S. Pat. No. 4,612,108 issued to Angevine et al., describes ahydrocracking process for feedstocks containing high boiling, waxycomponents using a number of sequential beds of hydrocracking catalystbased on zeolite beta. The proportion of zeolite beta in the catalystincreases in sequence so that the final bed has the highest zeoliteconcentration. The dewaxing activity of the zeolite beta-containingcatalysts is stated to be enhanced by the use of sequential beds in thismanner. The pour point of the high boiling fraction is reduced, as wellas that of the distillate product, permitting part of the high boilingfraction to be included in the distillate product, thereby increasingthe useful distillate yield.

U.S. Pat. No. 4,568,655, issued to Oleck et al. discloses a singlecatalyst system which is capable of demetalizing, hydrotreating andhydrodewaxing petroleum residue in a single stage process. The catalystsystem utilized includes one or more metal oxides or sulfides of GroupVIA and Group VIII of the periodic table impregnated on a base ofrefractory oxide material and zeolite beta. The catalyst also has about75% of its pore volume in pores no greater than 100 Å units in diameterand about 20% of its pore volume in pores greater than about 300 Å unitsin diameter.

U.S. Pat. No. 4,301,316 issued to Young, relates to a process for theselective alkylation of substituted or unsubstituted benzene compoundswith relatively long chain length alkylation agents to producephenylalkanes having an improved yield of the more external phenylisomers. The reaction can be carried out in the presence of acrystalline zeolite catalyst such as zeolite beta.

U.S. Pat. No. 4,501,926, issued to LaPierre et al., discloses thatpetroleum distillate feedstocks may be effectively dewaxed byisomerizing the waxy paraffins without substantial cracking. Theisomerization is carried out over zeolite beta as a catalyst and may beconducted either in the presence or absence of added hydrogen. Thecatalyst may include a hydrogenation/dehydrogenation component such asplatinum or palladium in order to promote the reactions which occur. Thehydrogenation/dehydrogenation component may be used in the absence ofadded hydrogen to promote certain hydrogenation/dehydrogenationreactions which will take place during the isomerization.

U.S. Pat. No. 4,518,485, issued to LaPierre et al., relates to a processfor dewaxing a hydrocarbon feedstock with a relatively high pour pointand containing paraffins selected from the group of normal paraffins andslightly branched paraffins and sulfur and nitrogen compounds whichcomprises subjecting said oil to hydrotreating in a hydrotreating zoneoperated at hydrotreating conditions sufficient to remove at least aportion of said sulfur and nitrogen compounds and subjecting saidhydrotreated oil to catalytic dewaxing by contacting said oil with acatalyst comprising zeolite beta having a silica/alumina ratio of atleast 30:1 and a hydrogenation component under isomerization conditions.

U.S. Pat. No. 4,554,065, issued to Albinson et al. describes a processfor dewaxing a hydrocarbon feedstock with a relatively high pour pointand containing paraffins selected from the group of normal paraffins andslightly branched paraffins which comprises subjecting said feedstock tocatalytic dewaxing at catalytic dewaxing conditions by passing saidfeedstock, along with hydrogen, over a dewaxing catalyst comprisingzeolite beta having a noble metal hydrogenation/dehydrogenationcomponent to produce a partially dewaxed product and subjecting saidpartially dewaxed product to catalytic dewaxing at catalytic dewaxingconditions by passing said partially dewaxed product over a catalystcomprising zeolite beta having a base metalhydrogenation/dehydrogenation component to recover a substantiallydewaxed product as a product of the process.

European Patent Application No. 0 159 846, European Patent ApplicationNo. 0 164 939 and European Patent Application No. 0 164 208 discloseparticular preparation methods of zeolite beta and the use of zeolitebeta in hydroisomerization of normal paraffins, when provided with ahydrogenation component, e.g., platinum.

U.S. Pat. No. 4,647,368, issued to McGuiness et al., describes anupgrading process for paraffinic naphthas which subjects a full rangenaphtha to hydrocracking over a zeolite beta hydrocracking catalyst toeffect a selective partial hydrocracking in which the higher molecularweight n-paraffinic components of the naphtha are hydrocrackedpreferentially to the lower molecular weight components with concurrentisomerization of n-paraffins to isoparaffins, to form a hydrocrackedeffluent which comprises isobutane, C₅ -C₇ paraffins and relativelyhigher boiling naphthenes and paraffins. The hydrocracked effluent issplit to remove the isobutane and the C₅ and C₇ paraffins with thebalance of the higher boiling components being used as a reformer feed.Removal of the C₅ and C₇ paraffins permits improved reformer operationwith the production of a higher octane product. The isomerization of theparaffins which occurs in the hydrocracking step provides a C₅ -C₇paraffinic fraction which is of relatively higher octane number becauseof the shift to isoparaffins, permitting this component to be used as agasoline blending component.

U.S. Pat. No. 4,845,063, issued to Chu, teaches a zeolite containing ametal of Group IB which preferably is silver. The zeolite may beactivated by heating in an inert atmosphere at 540° C.,ammonium-exchanged followed by calcination at 540° C. in air. Afterloading with silver the zeolite is calcined at 540° C. to 900° C.,preferably at 750° C. to 875° C.

U.S. Pat. No. 5,011,805, issued to Dessau, discloses a non-acidicreforming catalyst containing zeolite beta and a Group VIII metal whichpreferably is platinum. The zeolite containing the Group VIII metal issubjected to thermal treatment at a temperature between 150° and 500° C.

It can be seen from the disclosures of the above-cited patents thatzeolite beta has been prepared for use as a catalyst in varioushydrocarbon-conversion processes. However, none of the referencesdisclose zeolite beta having the unique characteristics of the presentinvention which provide particular utility in hydrocarbon-conversionprocesses.

SUMMARY OF THE INVENTION

The present invention relates to a crystalline microporousthree-dimensional solid catalyst having the structure and composition ofzeolite beta whose catalytic activity is enhanced by a method comprisingheating the catalyst in air or an inert atmosphere at a temperatureeffective to result in a very low concentration of strong acid speciesand a high concentration of weak acid species.

More specifically, a "volcano effect" is obtained on the activity of acrystalline microporous three-dimensional solid catalyst having thestructure and composition of zeolite beta, which previously had beensubjected to calcination by heating in air or an inert atmosphere at atemperature and for a period of time sufficient to oxidize at least asubstantial portion of a catalyst templating agent initially present onthe catalyst, by a method comprising the steps of: (1) ion-exchangingthe catalyst with a salt solution containing at least onehydrogen-forming cation other than hydronium; and (2) activating thecatalyst by heating in air or an inert atmosphere at a criticaltemperature of from about 600° to 675° C.

In another aspect of the invention there is provided a process for theconversion of hydrocarbons which comprises contacting a hydrocarbonfeedstock with an activated zeolite beta catalyst in a reaction zone athydrocarbon-conversion conditions wherein said zeolite beta catalyst hascatalytic activity enhanced by a method comprising heating the catalystin air or an inert atmosphere at a temperature effective to result in avery low concentration of strong acid species and a high concentrationof weak acid species.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 graphically illustrates the relationship between catalystcracking activity and catalyst activation temperature in a hydrocarbonconversion process using a zeolite beta catalyst that was calcined at600° C., ammonium-exchanged and activated.

FIG. 2 illustrates the relationship between isomerization and yield ofpentanes in a hydrocarbon conversion process using a zeolite betacatalyst that was calcined, ammonium-exchanged, platinum-exchanged andactivated.

FIG. 3 illustrates the relationship between isomerization and yield ofhexanes in a hydrocarbon conversion process using a zeolite betacatalyst that was calcined, ammonium-exchanged, platinum-exchanged andactivated.

FIG. 4 illustrates the relationship between weak acid species, strongacid species and activation temperature for zeolite beta.

DETAILED DESCRIPTION OF THE INVENTION

The crystalline microporous three-dimensional solids having thestructure and composition of zeolite beta (hereinafter also denoted as"zeolite beta") employable in the catalyst compositions herein areconventional materials and are described, for example, in above-citedU.S. Pat. No. 3,308,069 and U.S. Reissue Pat. No. 28,341 herebyincorporated by reference. Catalyst compositions for use in thehydrocarbon conversion processes described herein include zeolite betagenerally in conjunction with at least one inorganic oxide matrixcomponent as more fully described hereinafter.

The composition of zeolite beta in its as-synthesized form can berepresented as follows:

    [XNa(1.0 0.1--X)TEA] AlO.sub.2 YSiO.sub.2

where X is less than 1, preferably less than 0.75; TEA represents thetetraethylammonium ion from the templating agent; Y is greater than 5but less than 100. In the as-synthesized form, water of hydration mayalso be present in ranging amounts.

The sodium can be derived from the synthesis mixture used to preparezeolite beta. This synthesis mixture typically contains a mixture of theoxides (or of materials whose chemical compositions can be completelyrepresented as mixtures of the oxides) Na₂ O, Al₂ O₃, [(C₂ H₅)₄ N]₂ O,SiO₂ and H₂ O. Preferably, the mixture is held at a temperature of about75°-200° C. until crystallization occurs. The composition of thereaction mixture expressed in terms of mole ratios, preferably fallswithin the following ranges:

    SiO.sub.2 /Al.sub.2 O.sub.3-- 10 to 200;

Na₂ O/tetraethylammonium hydroxide (TEAOH)--0.0 to 0.1;

TEAOH/SiO₂ --0.1 to 1.0; and

H₂ O/TEAOH--20 to 75.

The product which crystallizes from the hot reaction mixture isseparated, suitably by centrifuging or filtration, washed with water anddried.

The material so obtained should then be calcined by heating preferablyin air or an inert atmosphere at a temperature usually within the rangeof from about 200° to about 1000° C. or higher, preferably from about550° to about 750° C., more preferably from about 575° to about 675° C.,and most preferably from about 600° to about 650° C., and for a periodof time preferably in excess of 0.25 hours, more preferably in excess of0.50 hours. The calcination should preferably not cause degradation ofany catalytic sites in zeolite beta. This calcination oxidizes and/ordecomposes at least a substantial portion of the catalyst templatingagent, e.g., tetraethylammonium ions or dibenzyldimethylammonium ionswhen used instead, or in addition to TEA, from the catalyst templatingagent, to hydrogen ions and removes the water to provide a zeolite betathat is substantially freed of templating agent. The calcined zeolitebeta is also known as H-form zeolite beta. As used herein, the terms "atleast a substantial portion" and "substantially freed" refer to at least50 wt. %, preferably at least 75 wt. % and most preferably 100 wt. %oxidation and/or decomposition of the catalyst templating agent from theas-synthesized zeolite beta.

With 100 wt. % oxidation and/or decomposition of the catalyst templatingagent, the formula of zeolite beta can then be depicted as follows:

    [XNa(1.0 0.1--X)H] AlO.sub.2 YSiO.sub.2

where X and Y are as defined above. The degree of hydration isconsidered to be zero following the calcination.

The H-form zeolite beta is then preferably ion-exchanged with a saltsolution containing at least one hydrogen-forming cation other thanhydronium, such as NH₄ ⁺ or quaternary ammonium, in which sodium isreplaced by the hydrogen-forming cation to give zeolite beta of theformula (anhydrous basis with NH₄ ⁺ exchange):

    [XNH.sub.4.sup.+ (10.1 --X)H] AlO.sub.2 YSiO.sub.2

where X and Y are as defined above.

According to this invention, the hydrogen-forming cation-exchanged formof zeolite beta may optionally be subjected to metal cation-exchange togive a material of the formula (anhydrous basis): ##EQU1## where X and Yare as described above and n is the valence of the metal M which may beany metal.

According to this invention, the hydrogen-forming cation-exchange formof zeolite beta or the metal cation-exchange form of zeolite beta canpreferably be combined with at least one inorganic oxide matrixcomponent and thereafter activated by heating in air or an inertatmosphere at a temperature and for a period of time sufficient toenhance at least one catalytic property of the catalyst in a hydrocarbonisomerization process as described hereinafter. The SiO₂ /Al₂ O₃ molarratio of zeolite beta product employed in this invention will generallybe in the range of from about 15:1 to about 45:1, preferably from about20:1 to about 30:1; and more preferably from about 22:1 to about 26:1.

Because a templating agent such as tetraethylammonium hydroxide is usedin its preparation, zeolite beta may contain occluded tetraethylammoniumions, e.g., as the hydroxide or silicate, within its pores in additionto that required by electroneutrality and indicated in the calculatedformulae herein. The formulae are calculated using one equivalent ofcation per aluminum atom in tetrahedral coordination in the crystallattice.

Zeolite beta, in addition to possessing a composition as defined above,may also be characterized by its X-ray diffraction data which are setout in U.S. Pat. No. 3,308,069 and U.S. Reissue Pat. No. 28,341. Thesignificant d values (Angstroms, radiation: K alpha doublet of copper,Geiger counter spectrometer) are as shown in Table 1 below:

                  TABLE 1    ______________________________________    d Values of Reflections in Zeolite Beta    ______________________________________    11.40 + 0.2     7.40 + 0.2     6.70 + 0.2     4.25 + 0.1     3.97 + 0.1     3.00 + 0.1     2.20 + 0.1    ______________________________________

As indicated above, zeolite beta is preferably ion-exchanged followingcalcination to remove the organic template by contacting (with orwithout the presence of an inorganic oxide matrix component) saidzeolite beta with a salt solution of at least one hydrogen-formingcation, such as NH₄ ⁺ or quaternary ammonium. Zeolite beta mayoptionally be metal cation-exchanged following the hydrogen-formingcation-exchange. Suitable metal cations include cations selected fromthe group consisting of cations of Group IIA, Group IIIA, GroupsIIIB-VIIB, e.g., nickel, cobalt, iron, manganese, copper, platinum,palladium, rhodium and the like including mixtures thereof, and rareearth cations selected from cerium, lanthanum, praseodymium, neodymium,promethium, samarium, europium, gadolinium, terbium, dysprosium,hoimium, erbium, thulium, ytterbium, lutetium and mixtures thereof. Ofcourse, the metal cation present as a result of metal cation-exchangeshould have no substantial adverse effect on the desired hydrocarbonconversion process. As a result of such ion-exchange, the zeolite betacan contain at least one cation, e.g., hydrogen-forming cation and/ormetal cation, which is different from the cations initially associatedwith zeolite beta as a result of its synthesis. The cation(s) present asa result of ion-exchange is preferably present in an effective amountbetween about 0.1 wt. % and about 20 wt. %, based on the weight of thestarting zeolite beta and is typically present in an effective amountbetween about 0.5 wt. % and about 10 wt. %.

The ion-exchange is generally carried out by preparing a slurry of thezeolite beta catalyst by adding about 5 to 15 volumes of water pervolume of catalyst, after which a solution of a selected cation isadded. The ion-exchange is generally carried out at room temperature andthe resulting solution is then heated to above about 50° C. and stirredat this temperature for about 0.5 to 3 hours. This mixture is thenfiltered and water washed to remove excess anion present as a result ofthe solution of the cation salt.

The zeolite beta is typically employed with at least one inorganic oxidematrix component, which combination is preferably formed afterion-exchange and prior to activation. While zeolite beta can be employedwith one or more of a wide variety of inorganic oxide matrix componentsas hereinafter described, it is important that the pore structure ofzeolite beta remain open and readily accessible to the feedstock inorder to provide effective catalytic activity. Illustrative inorganicoxide matrix components which may be employed in formulating catalysts,include: amorphous catalytic inorganic oxides such as catalyticallyactive silica/aluminas, clays, silicas, aluminas, silica-aluminas,silica-zirconias, silica-magnesias, silica-thorias, silica-berylias,silica-alumina-thorias, silica-alumina-zirconias, alumina-magnesias,alumina-borias, alumina-titanias and the like and mixtures thereof. Thematrix may be in the form of a sol, hydrogel or gel and is typically analumina, silica or silica-alumina component such as a conventionalsilica-alumina catalyst, several types available. The matrix may itselfprovide a catalytic effect, such as that observed for catalyticallyactive silica/aluminas, or it may be essentially inert. The matrix mayact as a "binder" in some instances although in some instances the finalcatalyst may be spray dried or formed without the need of a binder.

These matrix materials may be prepared as a cogel of silica and aluminaor as alumina precipitated on the preformed and preaged hydrogel. Silicamay be present as a major matrix component in the solids present in thematrix, e.g., present in an amount between about 5 and about 40 wt. %and preferably between about 10 and about 30 wt. %. The silica may alsobe employed in the form of a cogel comprising about 75 wt. % silica andabout 25 wt. % alumina or comprising about 87 wt. % silica and about 13wt. % alumina. The inorganic oxide matrix component will typically bepresent in the final catalyst in an amount between about 0 and 99 wt. %,preferably between about 5 and about 90 wt. %, based on the totalcatalyst. It is also within the scope of the instant invention to employother materials with the zeolite beta in the final catalysts, includingclays, carbon monoxide oxidation promoters, etc.

Representative of matrix systems employable herein are disclosed inBritish Patent Specification No. 1,315,553, published May 2, 1973 andU.S. Pat. Nos. 3,446,727 and 4,086,187, hereby incorporated byreference.

As above-mentioned, the catalysts of the present invention may beemployed with a matrix component and this may be a silica or aluminacomponent. The alumina component may comprise discrete particles ofvarious aluminas, e.g., pseudoboehmite. The alumina component may be inthe form of discrete particles having a total surface area, as measuredby the method of Brunauer, Emmett and Teller (BET), greater than about20 square meters per gram (M² /g), preferably greater than 145 M² /g,for example, from about 145 to about 300 M² /g. The pore volume of thealumina component will typically be greater than 0.35 cc/g. The averageparticle size of the alumina particles is generally less than 10 micronsand preferably less than 3 microns. The alumina may be employed alone asthe matrix or composited with the other matrix components.

The alumina component may be any alumina and has preferably beenpreformed and placed in a physical form such that its surface area andpore structure are stabilized so that when the alumina is added to animpure, inorganic gel containing considerable amount of residual solublesalts, the salts will not alter the surface and pore characteristicsmeasurably nor will they promote chemical attack on the preformed porousalumina which could undergo change. For example, the alumina istypically an alumina which has been formed by suitable chemicalreaction, the slurry aged, filtered, dried, washed free of residual saltand then heated to reduce its volatile content to less than about 15 wt.%. The alumina component may be present in the final catalyst in anamount ranging between about 5 and about 95 wt. %, preferably betweenabout 10 and about 30 wt. % based on the total catalyst. Further, analumina hydrosol or hydrogel or hydrous alumina slurry may be used inthe catalyst preparation.

Mixtures of zeolite beta and one or more inorganic oxide matrixcomponents may be formed into a final form for the catalyst by standardcatalyst forming techniques including spray drying, pelleting, extrusionand other suitable conventional means. The use of spray dryingprocedures is the preferred means by which catalysts are prepared andsuch procedures are well known in the art. When the catalyst is formedas extruded pellets and dried in air, such are typically crushed andsized to a size less than 150 microns.

Catalysts containing zeolite beta may be prepared by any conventionalmethod. One method of preparing such catalysts employing silica-aluminaand porous alumina is to react sodium silicate with a solution ofaluminum sulfate to form a silica/alumina hydrogel slurry which is thenaged to give the desired pore properties, filtered to remove aconsiderable amount of the extraneous and undesired sodium and sulfateions and then reslurried in water. The alumina may be prepared byreacting solutions of sodium aluminate and aluminum sulfate undersuitable conditions, aging the slurry to give the desired poreproperties of the alumina, filtering, drying, reslurry in water toremove sodium and sulfate ions and drying to reduce volatile mattercontent to less than 15 wt. %. The alumina may then be slurried in waterand blended in proper amounts, with a slurry of impure silica-aluminahydrogel. The zeolite beta may then be added to this blend. A sufficientamount of each component is utilized to give the desired finalcomposition. The resulting mixture is then filtered to remove a portionof the remaining extraneous soluble salts therefrom. The filteredmixture is then dried to produce dried solids. The dried solids aresubsequently reslurried in water and washed substantially free of theundesired soluble salts. The catalyst is then dried with or without heatto a residual water content of less than about 15 wt. %. The catalyst isemployed after activation as described hereinbelow.

For purposes of the present invention, the zeolite beta catalyst must beactivated by heating in air or an inert atmosphere at an initialtemperature effective to form an initial concentration of weak acidspecies and strong acid species and continuing said heating at anactivation temperature effective to substantially reduce theconcentration of strong acid species without substantially reducing theconcentration of weak acid species, both the weak acid and strong acidspecies being present in the catalyst prior to the activation.

Many of the references hereinbefore cited disclose that the zeolite betacatalyst should be activated at a temperature of about 540° C. Inaccordance with the present invention, it is preferred that theactivation temperature be effective to reduce the concentration ofstrong acid species by at least 50% as compared to the concentration ofstrong acid species remaining after activating at 540° C. Also, it ispreferred in accordance with the present invention that the activationtemperature be effective to increase the concentration of weak acidspecies as compared to the concentration of weak acid species remainingafter activating at 540° C. In general, the activation temperatures thatcorrespond to the range wherein the concentration of strong acid sitescan be substantially reduced without substantially reducing theconcentration of weak acid sites is at least about 600° C. and less thanabout 700° C. Preferably the activation temperature is from about600°-675° C., especially 625°-675° C.

Representative of the strong acid species are hydronium cations, i.e.,H₃ O⁺ and representative of the weak acid species are hydroxoaluminumcations, i.e., Al(OH)_(3-x) ^(x+). It is not critical to the presentinvention how the concentration of the respective acid species isdetermined. One suitable procedure is set forth in the followingreference; D. W. Breck and G. W. Skeels, ZEOLITE CHEMISTRY I, THE ROLEOF ALUMINUM IN THE THERMAL TREATMENT OF AMMONIUM EXCHANGED ZEOLITE Y,Proceedings of the Sixth International Congress on Catalysis, Vol. 2,pp. 645-659, The Chemical Society, London, (1977). This proceduregenerally involves treating the zeolite sample in a sodium chloridesolution and then titrating the sample with sodium hydroxide to obtaintwo end points, one at a low pH, i.e., the strong acid, and one at ahigh pH, i.e., the weak acid. A result in terms of milliequivalents ofsodium hydroxide per gram of zeolite can then be obtained for each acidspecies and translated to acid concentration.

The activation temperature is effective to reduce the concentration ofhydronium cations after activation to a level corresponding to less than0.2 milliequivalents of NaOH per gram of zeolite beta, and preferably tobelow 0.1 meq NaOH/gram. Even more preferably, the activationtemperature is effective to substantially eliminate the hydroniumcations to below detectable levels by the above infraction procedure. Itis further preferred that the concentration of hydroxoaluminum cationsafter activation is increased to a level of at least 0.8milliequivalents of NaOH per gram of zeolite beta, and especially to alevel of 0.9 meq NaOH/gram or more.

When a zeolite beta catalyst is prepared and activated according to theinvention, a rapid increase, or "volcano effect", is observed incatalytic activity. The activity kA according to the butane-crackingtest described hereinbelow may be increased to about 170 or higher,often to at least 200, and perhaps to 250 or more.

The activation time period is not narrowly critical and typically is inexcess of 0.25 hours, preferably in excess of 0.50 hours, so long as theactivation period is not sufficient to destroy the crystallinity ofzeolite beta. Activation of zeolite beta catalyst for a period of about1 hour or longer is a preferred aspect of this invention.

It is important to note that the method of the present invention can beperformed on a zeolite beta-containing catalyst in any of its stages ofexistence beyond the as-synthesized stage. That is, the method of thepresent invention can be performed on zeolite beta in the as-synthesizedform, calcined form or in the ion-exchanged form. Moreover, it is to befurther understood that the method of the present invention can be usedto treat regenerated catalysts as well, e.g., catalysts that have beensubjected to oxidative regeneration for carbon removal.

Hence, in one aspect of the present invention, the calcination step canbe included in the method, along with ion-exchange and activation stepsdescribed above. Thus, the present invention can be practiced onas-synthesized zeolite beta which contains templating agent by includingthe calcination step in the process.

In another aspect of the present invention, it is not required that thecalcination step be performed. For example, a catalyst supplier mayprovide zeolite beta that has been previously calcined. In such a case,the method would include the ion-exchange step and the activating stepas described above.

In still yet another aspect of the present invention, it is not requiredto perform the ion-exchange step. This would be appropriate when thezeolite beta has already been ion-exchanged as described above andperhaps dried such as when the catalyst is ready for loading in areactor vessel.

According to the present invention, in a process for catalyticallyconverting a feedstock into a product, a feedstock is contacted with theactivated zeolite beta catalyst in a reaction zone at conditionseffective to convert the feedstock into a product.

Substantially any feedstock or combination of feedstocks may be employedin the present invention. Such feedstock, i.e., reactant component orcomponents, may be gaseous, solid or liquid at ambient conditions, i.e.,20° C. and atmospheric pressure. The feedstock may be organic or acombination of inorganic and organic components. The present reactionsystem is particularly applicable to organic feedstocks, preferablyhaving molecules comprising carbon and hydrogen, and optionally one ormore other elements. This other element is preferably selected from thegroup consisting of oxygen, sulfur, halogen, nitrogen, phosphorus andmixtures thereof, with oxygen being particularly preferred.

The product or products obtained from the feedstock/activated zeolitebeta catalyst contacting will, of course, depend, for example, on thefeedstock, catalyst and conditions employed. As with the feedstock, theproduct or products can be organic or a combination of inorganic andorganic components. Preferably, the desired product is organic. However,it should be noted that a necessary, and therefore desired, reactionby-product may be inorganic even when the primary product sought isorganic. This is exemplified by the conversion of methanol to lightolefins plus water. The organic product or products have molecules whichpreferably include carbon and hydrogen. The desired product or productspreferably have kinetic diameters which allow such product or productsto be removed from or escape from the pores of the zeolite beta catalystcomposition.

The amount of zeolite beta catalyst in the reaction zone may vary over awide range depending, for example, on the specific processingapplication involved.

In addition to the feedstock, a diluent may be used in conjunction withthe feedstock if desired and/or beneficial to the overall process. Suchdiluent may be mixed or combined with the feedstock prior to thefeedstock/activated zeolite beta catalyst contacting or it may beintroduced into the reaction zone separately from the feedstock. Suchdiluent preferably acts to moderate the rate, and possibly also theextent, of feedstock chemical conversion and may also act to aid intemperature control. In certain embodiments, the diluent is preferablysubstantially continuously fed to the reaction zone during the process.Typical of the diluents which may be employed in the instant process arehelium, argon, nitrogen, carbon monoxide, carbon dioxide, hydrogen,hydrocarbons and mixtures thereof. The amount of diluent employed, ifany, may vary over a wide range depending on the particular applicationinvolved. For example, the amount of diluent may be in an amount in therange of about 0.1% or less to about 100 times or more of the moles offeedstock.

The conversion conditions at which the process occurs can vary widelydepending, for example, on the specific feedstock and catalyst employedand on the specific product or products desired. The present process isparticularly applicable with feedstock/activated zeolite beta catalystcontacting temperatures in excess of about 50° C., more preferably inexcess of about 100° C., and with pressures of from about atmospheric toabout 2000 psig. The residence time of the feedstock in the reactionzone may be independently selected depending, for example, on thespecific feedstock and catalyst employed, and on the specific product orproducts desired.

Preferably the organic feedstock is a hydrocarbon feedstock and thecatalytic-conversion process is a hydrocarbon-conversion process.Substantially any hydrocarbon-conversion process which is capable ofbeing catalyzed by a zeolite beta catalyst composition can be conductedin accordance with this invention. Illustrative of such hydrocarbonconversion processes include, for example, cracking, hydrocracking,alkylation for both the aromatic and isoparaffin types, isomerizationincluding normal-paraffin or xylene isomerization, polymerization,reforming, hydrogenation, dehydrogenation, transalkylation,dealkylation, hydrodecyclization and dehydrocyclization.

Using activated zeolite beta catalyst compositions which contain ahydrogenation promoter such as platinum or palladium, heavy petroleumresidual stocks, cyclic stocks and other hydrocrackable charge stockscan be hydrocracked at temperatures in the range of 200°-450° C. usingmolar ratios of hydrogen to hydrocarbon in the range of between 2 and80, pressures between atmospheric and 200 bar, and a liquid hourly spacevelocity (LHSV) of from 0.1 to 20, preferably 1.0 to 10.

The activated zeolite beta catalyst compositions employed inhydrocracking are also suitable for use in reforming processes in whichthe hydrocarbon feedstocks contact the catalyst at temperatures of fromabout 350°-600° C. and hydrogen pressures of from 1 to 35 bar. LHSVvalues in the range of 0.1 to 10 and hydrogen to hydrocarbon molarratios in the range of 1 to 20, preferably between 4 and 12.

Other isomerization reactions are carried out under conditions similarto those described above for reforming, using somewhat more acidiccatalysts. Olefins are preferably isomerized at temperatures of200°-500° C., while heavy paraffins, naphthenes and alkyl aromatics areisomerized at temperatures of 300°-550° C. Particularly desirableisomerization reactions contemplated herein in addition to the normalparaffin isomerization described above include the conversion ofn-heptene and/or n-octene to isoheptenes, and isooctenes,methylcyclopentane to cyclohexane, meta-xylene and/or ortho-xylene topara-xylene, 1-butene to 2-butene and/or isobutene, n-hexene toisohexene, cyclo-hexene to methylcyclopentene, etc.

Isomerization of a C₈ -aromatics mixture containing ethylbenzene andxylenes is a particularly preferred use of the activated beta zeolite ofthe invention. Optimally the aforementioned C₈ aromatics comprise anon-equilibrium mixture, i.e., at least one C₈ -aromatic isomer ispresent in a concentration that differs substantially from theequilibrium concentration at isomerization conditions. Usually thenon-equilibrium mixture is prepared by removal of para- and/orortho-xylene from a fresh C₈ aromatic mixture obtained from aromaticsproduction. A suitable C₈ -aromatics feed mixture may containnonaromatic hydrocarbons, e.g., naphthenes and paraffins, in an amountup to 30 mass % of the total feed.

Contacting may be effected using the catalyst in a fixed-bed system, amoving-bed system, a fluidized-bed system, or in a batch-type operation,with a fixed-bed system being preferred considering simpler operationand avoidance of attrition losses. The feedstock and hydrogen-rich gasoptimally are preheated to the desired reaction temperature and thenpassed into an isomerization zone containing a fixed bed of catalyst.The conversion zone may be one or more separate reactors with suitablemeans therebetween to ensure that the desired isomerization temperatureis maintained at the entrance to each zone. The reactants may becontacted with the catalyst bed in either upward-, downward-, orradial-flow fashion, and the reactants may be in the liquid phase, amixed liquid-vapor phase, or a vapor phase when contacted with thecatalyst. Alkylaromatic-isomerization conditions as disclosedhereinabove comprise a temperature of from about 300° to 550° C.,pressure of from 1 to 35 bar, and LHSV in the range of 0.1 to 10 hr⁻¹.Hydrogen if present is supplied at a molar ratio to the C₈ -aromaticsfeedstock of 1 to 20.

The particular scheme used to recover an isomerized alkylaromaticproduct from the effluent of the reactors of the isomerization zone isnot deemed to be critical to the instant invention, and any effectiverecovery scheme known in the art may be used. Typically, after removalof light-hydrocarbon components by flash separation, the condensedliquid product then is fractionated to remove light and/or heavybyproducts and obtain the isomerized product. The product fromisomerization of C₈ aromatics usually contains a higher proportion ofpara-xylene than in the feedstock and is processed to selectivelyrecover the para-xylene isomer, optionally by crystallization. Selectiveadsorption is preferred using crystalline aluminosilicates according toU.S. Pat. No. 3,201,491. Improvements and alternatives within thepreferred adsorption recovery process are described in U.S. Pat. Nos.3,626,020, 3,696,107, 4,039,599, 4,184,943, 4,381,419 and 4,402,832,incorporated herein by reference thereto. Preferably, non-recovered C₈-aromatic isomers are recycled to extinction and thus are convertedeither to para-xylene or by side-reactions. Ortho-xylene separation,preferably by fractionation, also may be effected on the fresh C₈-aromatic feed or isomerized product, or both in combination, prior topara-xylene separation.

At somewhat higher temperatures, i.e., from about 350°-550° C.,preferably 450°-500° C. and usually at somewhat lower pressures withinthe range of about 1 to 5 bar, the same catalyst compositions are usedto hydroisomerize feedstocks containing heavier normal paraffins.Preferably, the heavy paraffin feedstock comprises normal paraffinshaving a carbon number range of C₇ -C₂₀. Contact time between thefeedstock and the catalyst is generally relatively short in order toavoid undesirable side reactions such as olefin polymerization andparaffin cracking. LHSV values in the range of 0.1 to 10, preferably 1.0to 6.0 are suitable.

The crystal structure of the activated zeolite beta catalysts and theiravailability in a form totally void of alkali metal content favor theiruse in the conversion of alkylaromatic compounds according to theisomerization process described above or disproportionation as describedhereinbelow. Suitable alkylaromatic-conversion conditions encompassingthese uses, as disclosed herein, encompass a temperature of from about200° to 550° C., a pressure of from 1 to 150 bar and a liquid hourlyspace velocity (LHSV) of from 0.1 to 15 hr⁻¹.

Another favored use for the activated zeolite beta of the invention inalkylaromatics conversion is the catalytic disproportionation oftoluene, ethylene, trimethyl benzenes, tetramethyl benzenes and thelike. Disproportionation of toluene yields primarily C₈ aromatics andbenzene. Disproportionation of C₉ aromatics such as trimethylbenzenes,methylethyl benzenes and propylbenzenes yields a range of lighter andheavier aromatic compounds. Disproportionation of a feedstock comprisingboth toluene and C₉ aromatics favors the formation of C₈ aromatics,particularly when lighter and heavier aromatics produced in thedisproportionation reaction are recycled. In the disproportionationprocess, isomerization and transalkylation can also occur. Group VIIInoble metal adjuvants alone or in conjunction with Group VIB metals suchas tungsten, molybdenum and chromium are preferably included in thecatalyst composition in amounts of from about 3 to 15 wt. % of theoverall composition. Extraneous hydrogen can, but need not, be presentin the reaction zone which is maintained atalkylaromatic-disproportionation conditions comprising a temperature offrom about 200°-400° C., pressures in the range of 5 to 150 bar and LHSVvalues in the range of 0.1 to 15.

Catalytic cracking processes are preferably carried out with activatedzeolite beta compositions using feedstocks such as gas oils, heavynaphthas, deasphalted crude oil residua, etc., with gasoline being theprincipal desired product. Temperature conditions of 450°-600° C., LHSVvalues of 0.5 to 10 and pressure conditions of from about atmospheric to4 bar are suitable.

Dehydrocyclization reactions employing paraffinic hydrocarbonfeedstocks, preferably normal paraffins having more than 6 carbon atoms,to form benzene, xylenes, toluene and the like are carded out usingessentially the same reaction conditions as for catalytic cracking. Forthese reactions it is preferred to use the activated zeolite betacatalyst in conjunction with a Group VIII non-noble metal cation such ascobalt and nickel.

In catalytic dealkylation wherein it is desired to cleave paraffinicside chains from aromatic nuclei without substantially hydrogenating thering structure, relatively high temperatures in the range of about450°-600° C. are employed at moderate hydrogen pressures of about 20 to70 bar, other conditions being similar to those described above forcatalytic hydrocracking. Preferred catalysts are of the same typedescribed above in connection with catalytic dehydrocyclization.Particularly desirable dealkylation reactions contemplated hereininclude the conversion of methylnaphthalene to naphthalene and tolueneand/or xylenes to benzene. For dealkylation as well as alkylationprocesses, the activated zeolite beta compositions having pores of atleast 5 ⊥ are preferred. When employed for dealkylation of alkylaromatics, the temperature is usually at least 175° C. and ranges up toa temperature at which substantial cracking of the feedstock orconversion products occurs, generally up to about 370° C. Thetemperature is preferably at least 230° C. and not greater than thecritical temperature of the compound undergoing dealkylation. Pressureconditions are applied to retain at least the aromatics feed in theliquid state. For alkylation the temperature can be as low as 120° C.but is preferably at least 175° C. In alkylation of benzene, toluene andxylene, the preferred alkylating agent is selected from olefins such asethylene and propylene.

In catalytic hydrofining, the primary objective is to promote theselective hydrodecomposition of organic sulfur and/or nitrogen compoundsin the feed, without substantially affecting hydrocarbon moleculestherein. For this purpose it is preferred to employ the same generalconditions described above for catalytic hydrocracking, and catalysts ofthe same general nature described in connection with dehydrocyclizationoperations. Feedstocks include gasoline fractions, kerosenes, jet fuelfractions, diesel fractions, light and heavy gas oils, deasphalted crudeoil residua and the like, any of which may contain up to about 5 wt. %of sulfur and up to about 3 wt. % of nitrogen.

The hydrocarbon-conversion processes may be carried out in a batch,semi-continuous, or continuous fashion. The processes can be conductedin a single reaction zone or a number of reaction zones arranged inseries or in parallel, or they may be conducted intermittently orcontinuously in an elongated tubular zone or a number of such zones.When multiple reaction zones are employed, it may be advantageous toemploy one or more of such zeolite beta catalyst compositions in seriesto provide for a desired product mixture. Owing to the nature of thehydrocarbon conversion process, it may be desirous to carry out thecertain processes by use of the zeolite beta catalyst compositions in adynamic (e.g., fluidized or moving) bed system or any system of avariety of transport beds rather than in a fixed bed system. Suchsystems would readily provide for any regeneration (if required) of thezeolite beta catalyst compositions after a given period of time. Ifregeneration is required, the zeolite beta catalyst compositions can becontinuously introduced as a moving bed to a regeneration zone wherethey can be regenerated, such as for example by removing carbonaceousmaterials by oxidation in an oxygen-containing atmosphere. In thepreferred practice of some hydrocarbon conversion processes, the zeolitebeta catalyst compositions will be subject to a regeneration step byburning off carbonaceous deposits accumulated during reactions.

According to a preferred aspect of this invention, a normal/non-normalparaffinic hydrocarbon feedstock is contacted with the activated zeolitebeta catalyst in a reaction zone at an isomerization temperature atleast 300° C. lower than the activation temperature and effective toconvert at least a portion of the normal paraffin hydrocarbons into anon-normal paraffin hydrocarbon product.

The hydrocarbon feedstock to the reactor generally comprises normalparaffins in the C₅ to about C₁₅ carbon atom range and is preferablycomposed principally of the various isomeric forms of saturatedhydrocarbons having from 5 to 6 carbon atoms. Such feedstocks arenormally the result of refinery distillation operations, and thus maycontain small amounts of C₇ and even higher hydrocarbons, but these arefrequently present, if at all, only in trace amounts. Olefinichydrocarbons are advantageously less than about 4 mol. % in thefeedstock. Aromatic and cycloparaffin molecules have a relatively highoctane number, but are to a substantial degree cracked and/or convertedinto molecules of much lower octane number in the isomerization process.Accordingly, the preferred feedstock should not contain more than about25 mol. % combined aromatic and cycloparaffinic hydrocarbons.Advantageously, the C₅ and C₆ non-cyclic paraffins comprise at least 75mol. % of the feedstock, with at least 25 mol. % being normal pentaneand/or normal hexane. A feedstock of the following composition istypical:

    ______________________________________    Components    Weight-%    ______________________________________    C.sub.4 minus  4.1    i-C.sub.5     24.5    n-C.sub.5     27.8    i-C.sub.6     27.4    n-C.sub.6     14.7    C.sub.7 plus   1.5    ______________________________________

In the foregoing description of the preferred feedstocks suitablytreated in accordance with the present process, the expression "thevarious isomeric forms of pentane and hexane" is intended to denote allthe branched chain and cyclic forms of the compounds, as well as thestraight chain forms. Also, the prefix notations "iso" and "i" areintended to be generic designations of all branched chain and cyclicforms of the indicated compound.

The conditions at which the normal-paraffin hydrocarbon isomerizationprocess occurs can vary widely. The isomerization reaction can beconducted over a wide range of temperatures, but, in general, in therange from about 90° to about 425° C. Preferably, the isomerizationtemperature is between about 120°-300° C. and more preferably betweenabout 150°-290° C. Space velocities from about 0.25 to about 5 liquidvolumes per hour of isomerizable normal-paraffin hydrocarbons per volumeof activated zeolite beta catalyst composition are preferred withreaction zone pressures preferably within the range from about 6.9 bar(100 psi) to about 69 bar (1000 psi). it is particularly desirable tocarry out the isomerization reaction in the presence of hydrogenpreferably in the range from about 0.5 to about 5 moles of hydrogen permole of isomerizable hydrocarbon. The function of the hydrogen isprimarily to improve catalyst life, apparently by preventingpolymerization of intermediate reaction products which would otherwisepolymerize and deposit on the activated zeolite beta catalystcomposition. It is not necessary to employ pure hydrogen since hydrogencontaining gases are suitable. Product separation facilities of theisomerization process, such as catalytic conversion of naphthas, aresuitable sources of hydrogen-rich gases. These hydrogen-rich gasestypically contain light hydrocarbons, e.g., C₁ -C₃, and may also containother compounds.

The normal-paraffin hydrocarbon conversion process may be carried out ina batch, semi-continuous, or continuous fashion. The process can beconducted in a single reaction zone or a number of reaction zonesarranged in series or in parallel, or it may be conducted intermittentlyor continuously in an elongated tubular zone or a number of such zones.When multiple reaction zones are employed, it may be advantageous toemploy one or more of such zeolite beta catalyst compositions in seriesto provide for a desired product mixture. Owing to the nature of thenormal paraffin hydrocarbon isomerization process, it may be desirous tocarry out the certain processes by use of the zeolite beta catalystcompositions in a dynamic (e.g., fluidized or moving) bed system or anysystem of a variety of transport beds rather than in a fixed bed system.Such systems would readily provide for any regeneration (if required) ofthe zeolite beta catalyst compositions after a given period of time. Ifregeneration is required, the zeolite beta catalyst compositions can becontinuously introduced as a moving bed to a regeneration zone wherethey can be regenerated, such as for example by removing carbonaceousmaterials by oxidation in an oxygen-containing atmosphere. In thepreferred practice of some normal paraffinic hydrocarbon isomerizationprocesses, the zeolite beta catalyst compositions will be subject to aregeneration step by burning off carbonaceous deposits accumulatedduring reactions.

Often, portions of the products from the isomerization process as wellas other hydrocarbon conversion processes are admixed in variousproportions, as blending components, as well as with other blendingcomponents to form motor fuels such as gasoline. The details of suchblending operations are well known to those in the refining industry andneed not be further disclosed herein.

The following examples are illustrative of this invention.

EXAMPLE 1

5.8 grams (anhydrous weight) of sodium aluminate was added to 55.6 gramsof 40% tetraethylammonium hydroxide (TEAOH) in a glass beaker andstirred at room temperature for a period of five minutes. The resultingmixture was heated with stirring to reflux and held for two minutes inorder to dissolve the sodium aluminate. The resulting solution was paleyellow and the sodium aluminate was incompletely dissolved. The glassbeaker was transferred to a cool stirring hot plate and cooled withstirring to room temperature. As the solution cooled, additional finesolids appeared in the solution which adhered to the bottom and sides ofthe glass beaker. The white solid was scraped from the sides of theglass beaker with a teflon spatula and stirred. Once the sodiumaluminate/TEAOH solution was cooled, 145.4 grams of Ludox LS silica wasadded gradually. The resulting slurry became very thick and additionalhand agitation with the teflon spatula was needed to maintain the mixingof the thickening gel. The gel was mixed on the magnetic stirrer for anadditional ten minutes after all the Ludox LS silica had been added. Thegel was divided in half and placed in separate teflon liners of about 93grams and 105 grams respectively. Each teflon liner was placed in astainless steel reactor and digested in an oven at a temperature of 150°C. After six days, the two reactors were removed from the oven andcooled overnight. The contents were combined and slurried with anadditional 200 milliliters of deionized water and filtered. The solidproduct was washed with deionized water to a pH<10. The product wasdried at room temperature and, when examined by X-ray powderdiffraction, gave the characteristic X-ray powder pattern of zeolitebeta. The yield of zeolite beta product was approximately 50 grams.Analyzed properties of the zeolite beta product were as follows:

    ______________________________________    Na.sub.2 O, wt. %                     0.47    (TEA).sub.2 O, wt. %                    18.27    (NH.sub.4).sub.2 O, wt.%                    --    Al.sub.2 O.sub.3, wt. %                     6.38    SiO.sub.2, wt. %                    75.27    (TEA).sub.2 O/Al.sub.2 O.sub.3                     1.18    (NH.sub.4).sub.2 O/Al.sub.2 O.sub.3                    --    SiO.sub.2 /Al.sub.2 O.sub.3                    20.01    ______________________________________

The zeolite beta product was then calcined in flowing air at atemperature of 600° C. for a period of 2 hours to decompose thetetra-ethylammonium cation. After cooling, the calcined zeolite betaproduct was exchanged with NH₄ NO₃ solution (5 grams NH₄ NO₃ per gram ofcalcined zeolite beta product) at reflux (3 times), washed in distilledwater and dried at room temperature. Analyzed properties of thecalcined, ammonium-exchanged zeolite beta product were as follows:

    ______________________________________           Na.sub.2 O, wt. %                     <0.03           (TEA).sub.2 O, wt. %                     --           (NH.sub.4).sub.2 O, wt. %                     2.69           Al.sub.2 O.sub.3, wt. %                     6.56           SiO.sub.2, wt. %                     89.46           (TEA).sub.2 O/Al.sub.2 O.sub.3                     --           (NH.sub.4).sub.2 O/Al.sub.2 O.sub.3                     0.81           SiO.sub.2 /Al.sub.2 O.sub.3                     23.15    ______________________________________

EXAMPLES 2-11

The calcined, ammonium-exchanged zeolite beta product prepared inExample 1 was tested for n-butane cracking activity utilizing acylindrical quartz tube reactor (254 millimeters in length and 10.3millimeters internal diameter). Normal-butane cracking activity isuseful screening test for catalytic activity and is indicative ofisomerization activity. Separate samples of the calcined,ammonium-exchanged zeolite beta product were tested for n-butanecracking activity. The reactor was loaded with 20-40 mesh (U.S.standard) particles of the calcined, ammonium-exchanged zeolite betaproduct in an amount of from 0.5 to 5 grams. The calcinedammonium-exchanged zeolite beta product was then activated in thereactor for a period of 1 hour in a stream of either flowing helium orflowing air at the activation temperature indicated in Table A. below.The reaction feedstock was a helium-n-butane mixture containing 2 mol. %n-butane and, after activation of the zeolite beta product, was passedthrough the reactor at a rate of 50 cubic centimeters per minute withthe reactor temperature maintained at 500° C. Analysis of the feedstockand the reactor effluent was carried out using conventional gaschromatography techniques. The reactor effluent was analyzed after 10minutes of on-stream operation. From the analytical data, apseudo-first-order rate constant (kA) was calculated. The results aregiven in Table A. The value of kA is an indication of the level ofcatalytic activity.

                  TABLE A    ______________________________________    Example           Activation   % Consumption                                    % i-Butane    No.    Temperature (°C.)                        of n-Butane in Product                                            kA    ______________________________________     2     500 Air      91.3        0.4     126     3     500 Helium   88.4        1.1     128     4     550 Air      89.1        0.2     132     5     550 Helium   --          --      --     6     600 Air      93.1        0.1     184     7     600 Helium   93.3        0.1     170     8     650 Air      98.6        0.0     245     9     650 Helium   99.7        0.0     305    10     700 Air      82.2        0.0      60    11     700 Helium   --          --      --    ______________________________________

The above results are plotted in FIG. 1. The activity was enhancedsubstantially at activation temperatures according to the invention,relative to higher and lower temperatures, such that a "volcano effect"of activity relative to temperature was observed.

EXAMPLES 12-17

In order to demonstrate improved catalytic results from high temperatureactivation of zeolite beta in accordance with the invention, a series ofn-butane cracking tests were conducted with LZ-202 for comparisonpurposes. LZ-202, an omega type zeolite synthesized in an organic freesystem, is a known active catalyst for hydrocarbon conversion reactions.LZ-202 is available from UOP, Des Plaines, Ill. Separate samples ofammonium-exchanged LZ-202 product were tested for n-butane crackingactivity in accordance with the procedure described in Examples 2-11above. The results are given in Table B below and show no unusual effectin regard to activity. Typically, a temperature of 550° C. in air isobserved with most catalytic materials to be the optimum activationtemperature for catalysis.

                  TABLE B    ______________________________________    Example           Activation   % Consumption                                    % i-Butane    No.    Temperature (°C.)                        of n-Butane in Product                                            kA    ______________________________________    12     500 Air      76.8        4.1      71    13     500 Helium   82.1        3.5      57    14     550 Air      85.5        3.1     100    15     550 Helium   74.1        4.0      60    16     600 Air      62.5        4.6      56    17     600 Helium   56.0        5.0      37    ______________________________________

EXAMPLE 18

51.74 grams (anhydrous weight) of sodium aluminate were added to 361.4grams of 40% tetraethylammonium hydroxide (TEAOH) and mixed on amagnetic stirrer for a period of five minutes at room temperature beforeheating to reflux. The sodium aluminate did not completely dissolve. Theresulting slurry was transferred to a plastic beaker and stirred with aHeidolph mixer fitted with a jiffy pain mix stirrer until it cooled. Asthe slurry cooled, additional precipitate formed. When cool, 945.1 gramsof Ludox LS silica were gradually added with stirring to the sodiumaluminate/TEAOH slurry. A very thick gel formed and additional handagitation was needed to keep the slurry mixing. After all the Ludox LSsilica had been added, the gel was mixed for a period of five minutesand it thinned slightly. 1295.5 grams of the gel were transferred to atwo liter reactor and digested for a period of seven days at atemperature of 155° C. The reactor was then cooled overnight. Initialfiltration was slow, but as the product was washed with deionized water,filtration became easier. After washing until the pH of the filtrate wasless than 10, the solid product was dried at room temperature and fullycharacterized. This preparation had a yield of 350 grams. It had thecharacteristic X-ray powder pattern of zeolite beta. Analyzed propertiesof the zeolite beta product were as follows:

    ______________________________________    Na.sub.2 O, wt. %                     0.85    (TEA).sub.2 O, wt. %                    15.63    (NH.sub.4).sub.2 O, wt. %                    --    Al.sub.2 O.sub.3, wt. %                     6.12    SiO.sub.2, wt. %                    77.40    (TEA).sub.2 O/Al.sub.2 O.sub.3                     0.94    (NH.sub.4).sub.2 O/Al.sub.2 O.sub.3                    --    SiO.sub.2 /Al.sub.2 O.sub.3                    21.44    ______________________________________

The zeolite beta product was then calcined in flowing air at atemperature of 600° C. for a period of 2 hours to decompose thetetra-ethylammonium cation. After cooling, the calcined zeolite betaproduct was exchanged with NH₄ NO₃ solution (5 grams NH₄ NO₃ per gram ofcalcined zeolite beta product) at reflux (3 times), washed in distilledwater and dried at room temperature. Analyzed properties of thecalcined, ammonium-exchanged zeolite beta product were as follows:

    ______________________________________           Na.sub.2 O, wt. %                     <0.03           (TEA).sub.2 O, wt. %                     --           (NH.sub.4).sub.2 O, wt. %                     2.78           Al.sub.2 O.sub.3, wt. %                     6.03           SiO.sub.2, wt. %                     90.26           (TEA).sub.2 O/Al.sub.2 O.sub.3                     --           (NH.sub.4).sub.2 O/Al.sub.2 O.sub.3                     0.90           SiO.sub.2 /Al.sub.2 O.sub.3                     25.39    ______________________________________

EXAMPLES 19-28

Separate samples of the calcined, ammonium-exchanged zeolite betaproduct prepared in Example 18 were tested for n-butane crackingactivity in accordance with the procedure described in Examples 2-11above. The results are given in Table C below.

                  TABLE C    ______________________________________    Example           Activation   % Consumption                                    % i-Butane    No.    Temperature (°C.)                        of n-Butane in Product                                            kA    ______________________________________    19     500 Air      87.6        1.7     139    20     500 Helium   85.5        1.0     120    21     550 Air      85.2        0.5     123    22     550 Helium   --          --      --    23     600 Air      95.0        0.0     182    24     600 Helium   95.4        0.1     173    25     650 Air      98.1        0.0     210    26     650 Helium   97.6        0.0     230    27     700 Air      65.1        0.4      71    28     700 Helium   --          --      --    ______________________________________

In order to demonstrate the unique nature of this invention, thefollowing Examples 29-36 were conducted wherein the required activationstep or one or more of the preferred treatment steps were omitted, i.e.,calcination, and/or ion-exchange.

EXAMPLES 29-32

A zeolite beta product was prepared in accordance with the proceduredescribed in Example 18 above except without the final activating stepand without the ammonium exchange step. The zeolite beta product wastested for n-butane cracking activity in accordance with the proceduredescribed in Examples 2-11 above. The results are given in Table Dbelow. The results demonstrate inferior activity of this zeolite betaproduct in comparison with zeolite beta product prepared according tothis invention and further demonstrate the importance of the requiredcatalyst preparation step.

                  TABLE D    ______________________________________    Example           Calcination  % Consumption                                    % i-Butane    No.    Temperature (°C.)                        of n-Butane in Product                                            kA    ______________________________________    29     550 Air      23.5        6.9     22    30     600 Air      44.8        2.3     63    31     650 Air      33.9        3.6     43    32     700 Air      46.6        1.2     43    ______________________________________

EXAMPLE 33

A zeolite beta product was prepared in accordance with the proceduredescribed in Example 18 above except without the initial calcinationstep to oxidize the catalyst templating agent. The zeolite beta productwas ammonium-exchanged and activated at a temperature of 550° C. in airand thereafter tested for n-butane cracking activity in accordance withthe procedure described in Examples 2-11 above. The results are given inTable E below. The results demonstrate inferior activity of this zeolitebeta product in comparison with zeolite beta product prepared accordingto this invention and further demonstrate the importance of the requiredcatalyst preparation steps.

                  TABLE E    ______________________________________    Example           Activation   % Consumption                                    % i-Butane    No.    Temperature (°C.)                        of n-Butazne                                    in Product                                            kA    ______________________________________    33     550 Air      50.2        3.7     67    ______________________________________

EXAMPLE 34

A zeolite beta product was prepared in accordance with the proceduredescribed in Example 18 above except without the ammonium exchange step.Instead, the zeolite beta product was hydronium ion-exchanged after theinitial calcination step. The zeolite beta product was tested forn-butane cracking activity in accordance with the procedure described inExamples 2-11 above. The results are given in Table F below. The resultsdemonstrate that hydronium- exchanged zeolite beta results in inferioractivity in comparison with ammonium- exchanged zeolite beta.

                  TABLE F    ______________________________________    Example           Activation   % Consumption                                    % i-Butane    No.    Temperature (°C.)                        of n-Butane in Product                                            kA    ______________________________________    34     550 Air      3.5         2.1     4    ______________________________________

EXAMPLES 35-36

A zeolite beta product was prepared in accordance with the proceduredescribed in Example 18 above except the zeolite beta product washydrothermally treated with steam at a temperature of 600° C. followingthe ammonium exchange step. The product resulting from the steaming wasfully crystalline. The zeolite beta product was then activated at atemperature of 650° C. and thereafter tested for n-butane crackingactivity in accordance with the procedure described in Examples 2-11above. The results are given in Table G below. The results demonstratethat hydrothermal steam calcination or activation of zeolite betaproduct results in inferior activity in comparison with thermalcalcination or activation by heating in air or an inert atmosphere.

                  TABLE G    ______________________________________    Example           Activation   % Consumption                                    % i-Butane    No.    Temperature (°C.)                        of n-Butane in Product                                            kA    ______________________________________    35     650 Helium   2.8         21.1    2    36     650 Helium   5.1         18.8    3    ______________________________________

EXAMPLE 37

100 grams of calcined, ammonium-exchanged zeolite beta product preparedas in Example 18 were slurried in a beaker in one liter of distilledwater. A second solution containing 0.60 grams of Pt(NH₃)₄ Cl₂ dissolvedin 500 milliliters of distilled water was then added to the zeoliteslurry and the zeolite beta was platinum-exchanged. The resulting slurrywas then filtered and washed with distilled water, dried, extruded withpeptized alumina binder and dried again for a period of sixteen hours.The extrudates contained 0.32 wt. % platinum. The extrudates were splitinto two batches, one batch was calcined in air at a maximum temperatureof 650° C. (hereinafter Catalyst A) and the second batch was calcined inair at a maximum temperature of 540° C. (hereinafter Catalyst B).

EXAMPLE 38

Separate samples of Catalyst A and Catalyst B prepared in Example 37above were evaluated for C₅ /C₆ isomerization activity using a fixed bedmicroreactor unit comprising a stainless steel tube (5/8-inch internaldiameter). About 8.0 to 12.0 grams of selected Catalyst A or Catalyst B(40×60 mesh, U.S. Standard) were loaded in the microreactor and reducedunder a flow of hydrogen gas at a temperature of greater than 200° C.for a period of sixteen hours. A feed consisting of 60 wt. % n-C₅, 35wt. % n-C₆ and 5 wt. % cyclohexane was then introduced into themicroreactor at a reaction pressure of 250 psig, a weight hourly spacevelocity (WHSV) of 1.6 hr.⁻¹, a hydrogen/hydrocarbon feed molar ratio of2 and a reaction temperature specified in Table H below. Products werecollected at selected run times and the products were analyzed by gaschromatography. The products were evaluated in several respects bydetermining:

    ______________________________________    i-C.sub.5 Conversion                      =     i-C.sub.5                            i-C.sub.5 + n-C.sub.5    2,2-DMB (Dimethylbutane)                      =     2,2-DMB    Conversion              Total C.sub.6 Paraffins    ______________________________________

as a means to determine the relative extent of conversion of pentane andhexane to isomeric products. The results are set forth in Table H below.

                  TABLE H    ______________________________________           Reaction     i-C.sub.5 2,2-DMB    Catalyst           Temperature (°C.)                        Conversion                                  Conversion                                          C5.sup.+  Yield    ______________________________________    A      251.7        62.9      18.1    98.5    A      260.0        68.1      19.0    97.3    A      265.6        69.2      19.2    95.7    A      273.9        69.1      19.0    92.4    B      251.7        55.7      13.5    98.9    B      260.0        63.1      15.1    97.8    B      265.6        66.5      16.1    96.5    B      273.9        68.9      18.0    93.7    ______________________________________

The results set forth in Table H above are graphically illustrated inFIG. 2 and FIG. 3.

FIG. 2 graphically illustrates the relationship between C₅ isomerizationconversion and C₅ ⁺ yield as demonstrated by the isomerization processdescribed in Example 39, in particular, the relationship between wt. %i-C₅ of total C₅ paraffins and the wt. % C₅ ⁺ yield, utilizing a zeolitebeta catalyst activated at a temperature of 650° C., a zeolite betacatalyst activated at a temperature of 540° C. and a standard referencecatalyst as identified in Example 39.

FIG. 3 graphically illustrates the relationship between C₆ isomerizationconversion and C₅ ⁺ yield as demonstrated by the isomerization processdescribed in Example 39, in particular, the relationship between wt. %2,2-DMB (dimethylbutane) of total C₆ paraffins and the wt. % C₅ ⁺ yield,utilizing a zeolite beta catalyst activated at a temperature of 650° C.,a zeolite beta catalyst activated at a temperature of 540° C. and astandard reference catalyst as identified below.

It can be seen from FIGS. 2 and 3 that both the catalytic activity,i.e., conversion, and selectivity, i.e., yield, were substantiallyenhanced when the catalyst was activated at 650° C. as compared to 540°C. The delta i-C₅ conversion, delta 2,2-DMB conversion and delta RON(Research Octane Number) based on a standard reference catalyst werecalculated at 96% C₅ ⁺ yield using a 60:40 wt. % n-C₅ : n-C₆ feedcomposition as follows:

delta i-C₅ Conversion=i-C₅ conversion-63.00

delta 2,2-DMB Conversion=2,2-DMB conversion-17.00

delta RON=0.60×0.33 (i-C₅ conversion-63.00)+0.40×0.65 (2,2-DMBconversion-17.00)

The standard reference catalyst was HS-10, a platinum on H-mordenitecatalyst available from Shell Oil Company, The Hague, Netherlands,having an i-C₅ conversion of 63% and a 2,2-DMB conversion of 17%. In theformula; 0.60 and 0.40 denote the n-pentane and n-hexane composition ofthe feed in weight fraction, 0.33 denotes the RON octane differencebetween isopentane (RON=94) and normal pentane (RON=71) divided by 100,and 0.65 denotes the octane difference between 22DMB (RON=94) andn-hexane (RON=29) divided by 100. The results are set forth in Table Ibelow as follows:

                  TABLE I    ______________________________________            delta i-C.sub.5                           delta 2-2-DMB                                      Delta    Catalyst            Conversion     Conversion RON    ______________________________________    A       6.25           2.25       1.82    B       4.40           -0.39      0.80    HS-10   0.0            0.0        0.0    ______________________________________

The results from Table I show superior catalytic performance of zeolitebeta activated at a temperature of 650° C. in a C₅ /C₆ isomerizationprocess in comparison with the catalytic performance of the samecatalyst activated at a temperature of 540° C., the typical activationtemperature.

EXAMPLE 39

Approximately I gram samples on a dry weight basis of the ammoniumion-exchanged zeolite beta, as prepared in Example 1, were activated ina shallow bed under flowing dry air for 2 hours, removed from the ovenand placed in a desiccator to cool, then placed in a 50 ml solution of3.5 M NaCl solution. Potentiometric titrations were then developed with0.1 N NaOH solution. The result of the titrations shows the amount andtype of acidity developed by the zeolite under the various activationconditions.

Four samples were activated at 450, 540, 650° and 700° C. and thepotentiometric titrations for each sample were developed as describedabove. The results are plotted in FIG. 4. After 450° C. calcination, twotypes of acidity were determined, strong acidity from a hydrated proton,H₃ O⁺ and a weaker acid species of hydroxoaluminum cations, Al(OH)²⁺. Asthe activation temperature was increased, the amount of strong aciddecreased as the amount of the weaker acid species increased. Withoutbeing bound by any definitive theory, it can be observed that thedecrease in strong acidity is accompanied by an increase in weak aciditywhich corresponds well with the observed isomerization activity shown inExample 38 and FIGS. 2 and 3, and also the n-butane cracking activityshown in Examples 2-11. As the strong acidity (H₃ O⁺), decreases and theweak acidity increases (Al(OH)²⁺), the isomerization activity increases.Enhanced isomerization activity occurs when the strong acidity is nolonger observed in the titration and when the weak acidity is also at amaximum. As the weak acidity decreases with calcination above 650° C.,the isomerization activity will also be expected to decrease based onthe kA values for n-butane cracking, per Examples 2-11.

Although the invention has been illustrated by the preceding examples,it is not to be construed as being limited thereby; but rather, theinvention encompasses the generic area as hereinbefore disclosed.Various modifications and embodiments can be made without departing fromthe spirit and scope thereof. Accordingly, the Examples demonstratevarious ways in which the method of the present invention can provide azeolite beta-containing catalyst that can have at least one enhancedcatalytic property, e.g., reactivity, activity or selectivity, for usein hydrocarbon isomerization processes.

We claim:
 1. A process for the conversion of alkylaromatic compoundscomprising contacting the compounds at alkylaromatic-conversionconditions comprising a temperature of from about 200° to 500° C., apressure of from 1 to 150 bar and LHSV of from 0.1 to 15 hr⁻¹ with anactivated zeolite beta catalyst having a concentration ofhydroxoaluminum cations corresponding to at least 0.9 milliequivalentsof NaOH per gram of zeolite beta and a concentration of hydroniumcations corresponding to less than 0.1 milliequivalents of NaOH per gramof zeolite beta to obtain an alkylaromatic product.
 2. The process ofclaim 1 wherein the concentration of hydroninum cations in zeolite betais not detectable.
 3. The process of claim 1 wherein the catalystcomprises at least one inorganic oxide matrix component.
 4. The processof claim 3 wherein the matrix component is selected from the groupconsisting of silica, alumina, magnesia and mixtures thereof.
 5. Theprocess of claim 4 wherein the matrix component comprises alumina. 6.The process of claim 1 wherein the catalyst comprises one or more metalsselected from the Group VIII noble metals.
 7. The process of claim 6wherein the catalyst further comprises one or more Group VIB metals. 8.The process of claim 1 wherein a hydrogen diluent is used in conjunctionwith the alkylaromatic compounds.
 9. The process of claim 1 wherein theconversion comprises isomerization at alkylaromatic-isomerizationconditions to obtain an isomerized alkylaromatic product.
 10. Theprocess of claim 9 wherein the alkylaromatic compounds comprise a C₈-aromatics mixture and the isomerized product contains a higherproportion of para-xylene than in the feedstock.
 11. A process for theisomerization of a C₈ -aromatics feedstock comprising contacting thefeedstock at alkyl, aromatic-isomerization conditions with an activatedzeolite beta catalyst having a concentration of hydroxoaluminum cationscorresponding to at least 0.9 milliequivalents of NaOH per gram ofzeolite beta and a concentration of hydronium cations corresponding toless than 0.1 milliequivalents of NaOH per gram of zeolite beta toobtain an isomerized C₈ -aromatics product containing a greaterproportion of para-xylene than in the feedstock.
 12. The process ofclaim 11 wherein the alkylaromatic-isomerization conditions comprise atemperature of from about 300° C. to 550° C., pressure of from 1 to 35bar, and LHSV in the range of 0.1 to 10 hr⁻¹.
 13. The process of claim12 wherein hydrogen is present in a molar ratio to the C₈ -aromaticsfeedstock of 1 to
 20. 14. The process of claim 11 wherein the feedstockcomprises a non-equilibrium mixture of C₈ aromatics.
 15. The process ofclaim 11 further comprising recovery of para-xylene from the isomerizedC₈ -aromatics product.